1. Field of the Invention
The present invention relates to a driving mechanism of air mixing doors and a single hot water valve for adjusting a flow amount of hot water flowing into a heater core in an air-mixing type vehicle air conditioner.
2. Description of Related Art
In a conventional vehicle air conditioner, an air mixing system is generally used as an air temperature control method. In the air mixing system, a flow amount ratio of hot air heated by a heater core to cool air bypassing the heater core is adjusted by an air mixing door. Further, in the air mixing system, a hot water valve for adjusting a flow amount of hot water (engine cooling water) flowing into the heater core is not required to control an air blowing temperature, but the hot water valve is provided in many cases for the following reasons.
First, in a maximum cooling, an air passage of the heater core is entirely closed by the air mixing door, and a bypass passage through which air bypasses the heater core is entirely opened by the air mixing door. If the hot water valve is not provided in the air mixing system, high-temperature hot water continues to flow into the heater core even in the maximum cooling. Therefore, air around the heater core is heated by the high-temperature hot water in the heater core, and the heated air is mixed into cool air flowing through the bypass passage due to the natural convection. Thus, the air temperature to be blown into a passenger compartment is increased, thereby reducing the maximum cooling performance. Accordingly, in the maximum cooling, the hot water valve is provided to be entirely closed so that high-temperature hot water is prevented from flowing into the heater core.
Secondly, when the hot water valve is not provided, hot water from an engine continues to flow into the heater core even in the maximum cooling. At this time, since the air passage of the heater core is entirely closed by the air mixing door, the hot water returns to the engine without being cooled. Further, because the hot water flows into the heater core, a flow amount of hot water circulated to a radiator for cooling the hot water is reduced, and engine-cooling performance is reduced. When the hot water flowing into the heater core is stopped by entirely closing the hot water valve in the maximum cooling, the amount of hot water flowing into the radiator is increased, thereby increasing the engine-cooling performance.
In a general vehicle air conditioner including a single air mixing door, the air mixing door is simply coupled to the hot water valve so that the hot water valve is entirely closed when the air mixing door is operated at a maximum cooling position. However, in a vehicle air conditioner including plural air mixing doors, since operational positions (open degrees) of the air mixing doors are independently controlled, it is difficult to operatively link the plural air mixing doors and the single hot water valve. For example, in a right-left independent temperature control system, since the operational positions of the right and left air mixing doors are independently controlled, it is difficult to suitably control the operation of the hot water valve in accordance with the operation positions of the right and left air mixing doors.
On the other hand, if a dedicated driving mechanism only for driving the hot water valve is provided separately from the driving mechanism for the air mixing doors, because the dedicated driving mechanism for the hot water valve needs a servomotor and a link mechanism for opening and closing the hot water valve, production cost of a vehicle air conditioner is increased.